NCLEX Question of the Day – Saturday, April 04, 2026

Today’s question targets early recognition of magnesium sulfate toxicity in obstetric nursing. This matters because magnesium sulfate can protect a mother with severe preeclampsia from seizures, but the drug has a narrow safety margin. A nurse who notices subtle warning signs early can prevent respiratory failure and harm to both mother and baby.

Clinical Scenario

A 29-year-old client who is 35 weeks pregnant is admitted to the labor and delivery unit with severe preeclampsia. Her blood pressure is 168/106 mm Hg, and she reports a persistent frontal headache and blurred vision. The provider prescribes a magnesium sulfate infusion for seizure prophylaxis. Four hours after the infusion starts, the nurse reassesses the client. She is drowsy but arouses to voice. Her respiratory rate is 10/min, urine output over the last 4 hours is 80 mL total, and deep tendon reflexes are difficult to elicit. Fetal heart rate is 140/min. The client’s oxygen saturation is 95% on room air.

The Question

Which action should the nurse take first?

Answer Choices

1. Increase the maintenance IV fluid rate to improve urine output
2. Stop the magnesium sulfate infusion and prepare to administer calcium gluconate
3. Reposition the client onto her left side and repeat the blood pressure in 15 minutes
4. Document the findings as expected effects of magnesium therapy and continue monitoring

Correct Answer

B. Stop the magnesium sulfate infusion and prepare to administer calcium gluconate

Detailed Rationale

This client is showing signs of magnesium sulfate toxicity. The key clues are respiratory depression, low urine output, and diminished deep tendon reflexes. These findings matter because magnesium is excreted through the kidneys. When urine output drops, the drug can build up in the body. As the level rises, the client can progress from lethargy and absent reflexes to severe respiratory depression, cardiac conduction problems, and cardiac arrest.

The nurse’s first priority is airway and breathing. A respiratory rate of 10/min is not a mild side effect that can wait. It is a warning sign that the medication may be suppressing the central nervous system too much. The nurse should stop the infusion immediately to prevent more magnesium from entering the bloodstream.

Next, the nurse should prepare to give calcium gluconate, the antidote for magnesium toxicity, per protocol or provider order. Calcium antagonizes the effects of magnesium at the neuromuscular junction and helps reverse dangerous depression of respirations and reflexes. At the same time, the nurse should notify the provider, stay with the client, apply oxygen if needed, and closely monitor respiratory status, pulse oximetry, level of consciousness, and fetal status.

The urine output also supports the concern for toxicity. This client produced 80 mL over 4 hours, which averages 20 mL/hour. In a client receiving magnesium sulfate, urine output is usually expected to stay at or above about 30 mL/hour. Lower output suggests reduced renal clearance, which increases the risk for accumulation.

Deep tendon reflexes are another important bedside check. Magnesium depresses the neuromuscular system. A decreasing or absent patellar reflex is often one of the earliest clinically visible signs that the level is becoming unsafe. That is why frequent assessment of reflexes is part of standard monitoring for clients receiving this medication.

What should the nurse assess, do, and monitor here?

• Assess respiratory rate, effort, oxygen saturation, lung sounds, level of consciousness, reflexes, and urine output.
• Stop magnesium sulfate right away.
• Prepare and administer calcium gluconate as ordered.
• Notify the provider and charge nurse promptly.
• Keep emergency equipment available in case respiratory support is needed.
• Continue fetal monitoring because maternal instability can affect uteroplacental perfusion.
• Review recent lab results if available, including serum magnesium and renal function.

The reason this is the first action is simple: untreated toxicity can become life-threatening quickly. You can reassess blood pressure and urine output after the immediate safety threat is addressed, but you should not continue an infusion that is likely causing respiratory compromise.

Why the Other Options Are Wrong

A. Increase the maintenance IV fluid rate to improve urine output

This does not address the immediate danger. The client is already showing probable magnesium toxicity. Giving more fluid without a specific order may worsen pulmonary edema risk, which is already a concern in severe preeclampsia. Low urine output here is a red flag, not just a hydration problem to fix independently.

C. Reposition the client onto her left side and repeat the blood pressure in 15 minutes

Left-side positioning can improve uteroplacental perfusion and is useful in hypertensive disorders of pregnancy. But it does not treat magnesium toxicity. The client’s most urgent problem is respiratory depression, not positioning.

D. Document the findings as expected effects of magnesium therapy and continue monitoring

Some effects of magnesium sulfate are expected, such as feeling warm, mild nausea, or some drowsiness. However, a respiratory rate of 10/min, reduced urine output, and diminished reflexes are not routine findings to simply watch. They suggest a serious adverse response that requires intervention.

Key Takeaways

• Magnesium sulfate is used in severe preeclampsia to prevent seizures, but it can become dangerous if it accumulates.
• Three high-yield toxicity signs are: respiratory rate less than 12/min, low urine output, and diminished or absent deep tendon reflexes.
• Kidney function matters because magnesium is cleared renally.
• The antidote is calcium gluconate.
• Use ABCs to set priorities. Respiratory compromise comes before routine reassessment.

• On-shift mini-checklist:
• Check respirations before and during the infusion.
• Track hourly urine output closely.
• Assess reflexes consistently, using the same technique each time.
• Keep calcium gluconate available per unit protocol.
• If toxicity is suspected: stop the infusion, stay with the client, call for help, and monitor mother and fetus closely.

Quick Practice Extension

1. A postpartum client receiving magnesium sulfate has a respiratory rate of 14/min, urine output of 35 mL/hour, and 2+ patellar reflexes but reports feeling flushed and mildly nauseated. Which finding is most reassuring, and why?

2. A client with severe preeclampsia on magnesium sulfate suddenly becomes difficult to arouse and has absent patellar reflexes. What additional assessment finding would most strongly support worsening toxicity?

Category: OB

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